Network Address and Port Translation
Network address (and Port) translation (NAPT) is a technique used to share one IP address amongst several computers. For most common applications, enabling NAPT on a specific interface is adequate. From then on, all clients behind the NAPT router automatically share the same IP address. To run a server behind a NAPT router, extra configuration is needed. On the NAPT page, you can specify these settings.
The NAPT web page contains four tabs:
NAPT Entries
Multi-NAT Entries
Default Server
UPnP
NAPT Entries
For outgoing connections, NAPT entries are created dynamically whenever information migrating through this connection tries to reach a foreign host. For incoming connections however this is not done, mainly for security reasons, so therefore the NAPT entries table allows you to specify static NAPT entries. A static NAPT entry will redirect all incoming connections on a specified address/port to an address/port in the local network.
The SpeedTouch can have multiple IP addresses, therefore you can specify the IP address in the Outside IP box on which to perform NAPT, and the Outside port. Using 0.0.0.0 as outside IP address causes a template to be created, which will be valid for every one of the SpeedTouch NAPT enabled IP addresses established AFTER the creation of the template. In the input boxes 'Inside IP' and 'Inside PORT' you can specify the local machine and port to which traffic needs to be redirected.
The Protocol selection box is used to specify the protocol of the traffic expected to be received on the inside IP
ORT. Keep in mind that the Inside and Outside Ports only need to be specified for the TCP and UDP protocols. All other protocols don't need a port to be specified.
Notice that saving static NAPT entries could be a problem if you work with dynamic IP addresses (for example, if you use a PPP link to connect to the internet, then the SpeedTouch will get a different IP address every time you establish a connection). In this case the only way to be able to save your settings is to use a template, so that you don't have to specify which SpeedTouch IP address to use.
Multi-NAT Entries
The Multi-NAT Entries table allows you to overview and add/delete network address mappings from inside (local) IP address (ranges) to outside (public) IP address (ranges).
While with Static NAPT entries both Network Address Translation as Port Translation (hence NAPT) is performed, Multi-NAT entries only perform network address translation leaving source and destination ports untouched.
Default Server
It is possible to specify a default server. All incoming connections will be forwarded to the IP address specified here. This setting should be adequate for most server applications.
UPnP
UPnP also provides NAPT Traversal: UPnP aware applications on a PC will automatically create NAPT entries on the SpeedTouch for incoming ports it needs. As a consequence these applications are able to traverse the SpeedTouch NAPT engine without the need for extra configuration: no NAPT algorithms - the so called NAPT Helper applications - are needed or activated. NAPT entries created by UPnP will be created as templates.
For security reasons you are able to configure the UPnP policy towards Windows XP and UPnP aware applications and Operating Systems. Select:
Full
Unlimited UPnP operation between a host running Windows XP and the SpeedTouch.
All UPnP-based communication between any local host and the SpeedTouch is allowed.
A local host is:
Allowed to connect/Disconnect the SpeedTouch Internet Gateway connection.
Allowed to add/delete NAPT port mappings for any host/application.
Secure
Limited UPnP operation between a host running Windows XP and the SpeedTouch.
UPnP-based communication between a local host and the SpeedTouch is limited, and host-specific restricted.
A local host is:
NOT allowed to connect/disconnect the SpeedTouch Internet Gateway connection.
Allowed to add/delete NAPT port mappings only for its own IP address, not for other local hosts.
Off
All UPnP support is disabled on the SpeedTouch. UPnP-based communication between a local host and the SpeedTouch is not possible.
DHCP
DHCP, short for Dynamic Host Configuration Protocol, is a client/server protocol designed for automatic configuration of TCP/IP hosts.
To make local or wide area networking a plug & play experience, the SpeedTouch IP host is able to support automatic IP parameter configuration (i.e. acting as DHCP client) or IP parameter distribution (i.e. acting as DHCP server or as DHCP Relay), on all configured interfaces (LAN and WAN).
Of course, if DHCP is not used on the network, you can also disable any DHCP feature of the SpeedTouch.
Although working in close combination, still the three DHCP entities the SpeedTouch supports, are capable of working fully independently from each other. You can perfectly run the SpeedTouch DHCP server on your local network, whilst having one or more SpeedTouch DHCP clients running on WAN interfaces and one or more SpeedTouch DHCP relays running on yet another set of WAN interfaces.
The DHCP web page offers three tabs to configure the SpeedTouch DHCP functionality:
DHCP Server
To configure the general behavior of the SpeedTouch DHCP server.
DHCP Relay
To configure the SpeedTouch DHCP relay.
DHCP Client
To configure the SpeedTouch DHCP client.
DHCP Server
Important Note: Always make sure that only one DHCP server is active at the time per (LAN or WAN) interface. Two servers being active simultaneously on the same link layer will most likely lead to unpredictable configurations.
The DHCP server configuration is split up in three sections:
Server Config
To configure the SpeedTouch DHCP server "master" settings and behavior.
Server Leases
To overview current the SpeedTouch DHCP server's current leases, and/or add/delete static DHCP lease entries.
Address Pools
To overview and add/delete DHCP address pools for the SpeedTouch DHCP server.
As mentioned before, the SpeedTouch DHCP server - configuring local network hosts - can be run in conjunction with one or more SpeedTouch DHCP clients or SpeedTouch DHCP Relay agents, each created on behalf of a wide area connection. I.e. for WAN interfaces the SpeedTouch offers DHCP client, or DHCP relay support to configure multiple Routed Ethernet (MER) or Routed IPoA interfaces independently.
Server Config
The server config tab allows you to:
Overview the current SpeedTouch DHCP Status
Enable or disable the SpeedTouch DHCP server
Enable or disable the SpeedTouch DHCP server's Auto-DHCP feature.
Depending on the DHCP server status, following messages may be shown:
Scanning for other DHCP server
In case the DHCP server and its Auto-DHCP feature are enabled, during local network probing on the SpeedTouch Ethernet interface 'eth0'.
DHCP server stopped - DHCP client
In case the DHCP server and its Auto-DHCP feature are enabled, and a concurrent DHCP server was found during network probing, thus causing its own DHCP server to be stopped and a DHCP client on the SpeedTouch Ethernet interface 'eth0' be created and activated
DHCP server started
In case the DHCP server and its Auto-DHCP feature are enabled, and no concurrent DHCP server was found during network probing, thus starting its own DHCP server on the SpeedTouch Ethernet interface 'eth0'.
DHCP server running
In case the SpeedTouch DHCP server is enabled by default (without Auto-DHCP).
DHCP client
In case the SpeedTouch DHCP server is disabled by default, and a DHCP client is running on the SpeedTouch Ethernet interface 'eth0'.
No DHCP
In case the SpeedTouch DHCP server is disabled by default and the SpeedTouch Ethernet interface 'eth0' IP address is statically assigned.
The radio buttons allow you to configure the working mode of the SpeedTouch DHCP server.
Select:
DHCP server ON
To enable the SpeedTouch DHCP server. In addition, select the appropriate Auto-DHCP operandus mode:
Auto-DHCP ON (and press Apply)
The SpeedTouch will not start its DHCP server immediately, but will first probe the network for a possible concurrent DHCP server for some period of time (set by client time-out in seconds). In case another DHCP server is found, the SpeedTouch DHCP server is not started, and a DHCP client will be created on its Ethernet interface instead.
If no concurrent DHCP server is found, the SpeedTouch DHCP server is started.
Auto-DHCP OFF (and press Apply)
The SpeedTouch DHCP server is started instantly, without checking the network first.
DHCP server OFF (and press Apply)
To disable the SpeedTouch DHCP server. If it was running, it will be stopped immediately.
Server Leases
In case the SpeedTouch DHCP server is running this table holds all leases which are assigned by the DHCP server to (accepted) DHCP clients.
Following lease parameters are shown :
Client ID
The identity of the DHCP client.
Address
The IP address leased by the DHCP client.
Pool
The DHCP server address pool from which the lease IP address is taken.
TTL
The DHCP server lease's Time To Live (in seconds).
For a permanent DHCP lease, TTL displays infinite.
State
The DHCP server lease state:
Free (in case of statically added DHCP leases)
Indicating an unused DHCP server leases. No DHCP request from this particular Client ID has been received by the DHCP server (yet).
Used
Indicating assigned DHCP leases. A DHCP lease has been assigned to this Client ID in the past (actually (Pool lease time)-TTL seconds ago).
As soon as a DHCP request is received, the SpeedTouch DHCP server will assign the IP address matching the DHCP client's identity to this client (e.g. in case of a renewal, or for static entries). If no pre-configured lease could be found in the table, a new lease will be created when the client's request is granted.
Existing DHCP leases can be made static (i.e. TTL infinite) by selecting the DHCP lease and clicking Lock.
DHCP leases can be added manually, e.g. for DHCP client devices that need a "static" IP configuration. You can also remove existing DHCP leases.
Address Pools
One or more disjunctive DHCP server address pools can be created per existing SpeedTouch interface using the DHCP Server Address Pool table. The first address pool displayed in the table has the highest priority for a certain interface. The DHCP server address pool table shows the following address pool parameters :
Name
The name of the DHCP server's address pool.
Interface
The SpeedTouch interface for which the address pool applies.
Start address
The start IP address of the DHCP server's address pool.
End address
The end IP address of the DHCP server's address pool. Both the start and end IP address define the IP address range used by the DHCP server to assign leases.
Subnet mask
The subnet mask of the DHCP server's address pool.
Lease time
The maximum time a client is allowed to use the address.
Gateway
The IP address that will be assigned to DHCP clients as there default gateway
Server
The SpeedTouch IP address used as DHCP server address (applicable for SpeedTouch multi-homing).
Primary DNS Server
The IP address of the primary DNS server.
Secondary DNS Server
The IP address of the secondary DNS server.
The table header shows following pool properties in addition :
State : the current DHCP server's address pool state.
PPP : the PPP interface used to fill the DHCP server's address pool dynamically (dynamic pools only).
Two kinds of DHCP server address pools can be envisaged : static and dynamic address pools. Static address pools are configured manually by the user (state = static); on the other hand dynamic pools are configured dynamically based on the PPP-IPCP parameters negotiated for a (Routed) PPP connection (PPP interface given in the PPP column). When the PPP connection is up (state = up), all pool properties are defined except for the lease time which has to be configured manually. At the moment the PPP connection goes down (state = down) the pool parameters are kept to preserve LAN connectivity. If the pool parameters have been changed after the PPP connection comes up again, all associated leases are updated as well.
DHCP Relay
In a basic DHCP scenario a DHCP client on a certain part of a network is always able to address a DHCP server residing in the same part of the network for completing its IP configuration.
The SpeedTouch DHCP Relay allows to extend the reach DHCP client requests from one connected link layer network (local or remote), via the SpeedTouch relay to another connected network - equipped with a DHCP server - not residing in the same link layer network.
The DHCP relay tab allows you to add/delete and overview SpeedTouch DHCP relay interfaces.
The DHCP relay configuration is split up in two sections:
Relay config
To add/delete and configure a DHCP relay server on a certain interface
Relay interfaces
To enable/disable and define the behavior of the DHCP relay agent per configured interface.
Relay config
The Relay Configuration table allows you to add or delete (additional) DHCP relay agents for a specific interface.
To create a new DHCP relay agent:
Click New
Enter the DHCP server IP address
Select the appropriate relay interface via the Interface drop down list (select 'None' to indicate no interface is specified).
Enter the Gateway IP address to be used for the giaddr field in relayed DHCP packets.
Click Apply.
Relay interfaces
The Relay interface table allows you to configure interface specific DHCP relay settings as:
Enable/disable the DHCP relay server
The maximum number of hops allowed for relayed DHCP requests and replies (as indicated in the DHCP packet)
Defining whether to forward (trusted) or to drop (not trusted) DHCP request packets when a DHCP relay agent info option is present and the Gateway IP address field is 0 (as specified in RFC3046).
Define the remote ID (as specified in RFC3046) to allow the DHCP relay agent to relay DHCP responses to the proper network.
DHCP Client
Dynamic interfaces are created and managed by means of the DHCP Client Configuration table. The following parameters are manageable by the user :
Interface
The name of the SpeedTouch logical interface for which this DHCP client applies
Address
The preferred IP address to be assigned to the DHCP client. If not accepted, the (remote) DHCP server may overrule this address.
Client ID
MAC address of the SpeedTouch logical interface, to be communicated to the (remote) DHCP server. If empty, the SpeedTouch MAC address is used.
Host name
The host name associated with the dynamic IP address, to be communicated to the (remote) DHCP server
Lease time
The preferred duration of the lease of the dynamic IP address, if assigned. If not accepted, the (remote) DHCP server may overrule this lease time.
Address translation
If selected, the dynamic IP address will be used in a NAPT context
The Address column shows the IP address assigned to the interface given in the first column.
The State column shows the current state of the dynamic interface. According to RFC2131, following states are envisaged:
init
The DHCP client hasn't been activated yet. (You can activate a DHCP client entry by selecting it and clicking Enable).
requesting
The DHCP client is searching for a DHCP server.
selecting
The DHCP client requests a server for an IP address.
bound
A dynamic IP address has been assigned by the DHCP server.
renewing
The DHCP client requests a known server to extend its lease.
rebinding
The DHCP client searches a server to extend its lease.
The Timeout column is filled in for each DHCP client which is currently in the bound state. It indicates the lease time of the assigned IP address.
DNS
DNS is short for Domain Name System. DNS is a network functionality that allows network members to use host names rather than IP addresses for referencing networked computers.
DNS in the SpeedTouch operates in close co-operation with DHCP. Basically the scenario is as follows:
Assume the SpeedTouch is up and running and configured as DHCP Server.
A PC on your local Ethernet segment, configured as DHCP client is powered on. During start-up it will issue a few DHCP requests. Besides asking for IP parameters, it reveals its computer or host name in these DHCP requests.
The SpeedTouch intercepts the requests and returns a DHCP reply. This reply contains IP parameters such as: IP address, Net mask, IP address of Default Gateway, IP Address of Primary DNS server and Domain Name to list a few.
During the request and replies, the SpeedTouch builds a tiny database containing hostnames and IP addresses. To give an example, the entry for a computer named "Pluto" will get the IP address 10.0.0.1.
If a computer on the local network references "Pluto", then the SpeedTouch resolves this name to IP address 10.0.0.1.
The DNS web page contains two tabs:
DNS Hostname Table
DNS Server Configuration
DNS Hostname Table
The DNS hostname table shows all DNS host names (with respective IP address) the SpeedTouch DNS server is aware of (e.g. entries created via DHCP server replies to leases).
If not all computers reveal their hostname in the DHCP request, or even worse if they do not support DHCP, static entries can be added to the local DNS database. To do so, click New; enter the IP address and corresponding host name of the computer and click Add. Care should be taken to keep the database consistent.
DNS Server Configuration
In addition to the host name, a local PC needs the DNS domain name to construct a fully qualified name. By default the SpeedTouch DNS' domain name is lan. You can specify another (sub)domain name in the domain field (and Apply).
In normal conditions you should never disable the SpeedTouch DNS server, surely not in case the SpeedTouch DHCP server is active on the local network as well. If required however, you can disable the SpeedTouch DNS server by deselecting Activate Server (and Apply).
Note: Disabling the SpeedTouch DNS server will disable all DNS forwarding functionality as well. This may compromise end-to-end connectivity through the SpeedTouch connections.